1. Field of the Invention
This present invention is directed to blowout preventers, to tubular-shearing blades for them, and methods of their use.
2. Description of Related Art
The prior art discloses a wide variety of blowout preventers and tubular-shearing blades for blowout preventer bonnets.
Typical blowout preventers have selectively actuatable rams in oppositely disposed bonnets secured to the body. The rams are either pipe rams (to contact, engage, and encompass pipe and/or tools to seal a wellbore) or shear rams (to contact and physically shear a tubular, casing, pipe or tool used in wellbore operations). Rams are usually positioned opposite each other on either side of a main body and can, upon activation and subsequent shearing of a tubular, seal against each other at a center of the main body over a center of a wellbore.
Typical rams include a ram block on which parts, e.g. seals and/or cutting blades, are releasably secured. Blowout preventers and tubular-shearing blades for them are disclosed in many U.S. patents, including, but not limited to, U.S. Pat. Nos. 3,946,806; 4,043,389; 4,313,496; 4,132,267, 4,558,842; 4,969,390; 4,492,359; 4,504,037; 2,752,119; 3,272,222; 3,744,749; 4,253,638; 4,523,639; 5,025,708; 5,056,418; 5,400,857; 5,575,452; 5,655,745; and 5,918,851; 4,313,496; 4,550,895; 5,360,061; 4,923,005; 4,537,250; 5,515,916; 6,173,770; 3,863,667; 6,158,505; 5,575,451; 4,057,887; 5,505,426; 3,955,622; 3,554,278; and 5,013,005.
There has long been a need, recognized by the present inventor for a blowout preventer which can effectively and efficiently shear tubulars, e.g. tubulars used in wellbore operations, including relatively large tubulars such as casing, drill collars, and drill pipe tool joints. In certain prior tubular shearing systems, a tool joint is located so that shearing rams do not encounter the tool joint, but shear only a relatively smaller portion of the tubular. Proper location takes time and, if a tool joint is improperly located, no or ineffectual shearing may result.